The present invention relates to a measurement device in an electronically controlled microwave ignition system of an internal combustion engine, suitable for measuring the ionization current of the gases in the cylinders of the engine and/or measuring the voltage at the terminals of the electrodes of an ignition spark plug during an ignition command.
The ionization current of the gases in the cylinders of the engine is typically measured after the end of ignition and finds particularly advantageous applications, for example for detecting the angle corresponding to the pressure peak of the combustion chamber, of pinking or else for the identification of misfires.
Circuits for measuring the ionization current for a conventional ignition system are known in which the operation consists in polarizing the mixture of the combustion chamber after the generation of the spark between the electrodes of the ignition spark plug, in order to measure the current resulting from the propagation of the spark.
Such circuits are conventionally placed at the foot of the secondary winding of an ignition coil connected to the spark plug.
These circuits however require being dedicated to the characteristics of conventional ignition and are therefore not adaptable as such to plasma-generation ignition systems, using ignition spark plugs of the microwave coil-on-plug type (BME), as described in detail in the following patent applications filed in the name of the applicant, FR 03-10766, FR 03-10767 and FR 03-10768.